I've been following the work of Auricle Inc., a company commercializing decades of neuroscience research out of Dr. Susan Shore's lab at the University of Michigan. (Full disclosure: I have spoken to their CEO about potentially helping with their funding, although my primary concern is getting their product to the public).
Instead of just masking the sound, their device targets the root cause using bimodal neuromodulation. It pairs specific audio tones with mild electrical pulses to the jaw/neck to desynchronize hyperactive neurons in the dorsal cochlear nucleus.
Here are the two papers that cover the underlying science, and go over the efficacy:
The foundational mechanism and Phase 1 trial showing how it induces long-term depression (LTD) in the brain circuitry: https://www.science.org/doi/10.1126/scitranslmed.aal3175
The Phase 2 double-blind, randomized clinical trial results showing significant reductions in tinnitus loudness and burden: https://jamanetwork.com/journals/jamanetworkopen/fullarticle...